These days, in particular, a color image-forming material is the mainstream of an image-recording material; and concretely, inkjet-type recording materials, thermal transfer-type recording materials, electrophotographic recording materials, transfer-type silver halide photosensitive materials, printing inks and recording pens are much used. In an image sensor such as CCD as photography machinery and in LCD or PDP as displays, a color filter is used for recording and reproducing color images.
In a color image-recording material and a color filter, used are colorants (dyes, pigments) of three primary colors for an additive mixture process or a subtractive mixture process. At present, however, no one could find a fast colorant that has absorption characteristics capable of realizing a favorable color reproduction range and is durable to various conditions in practical use, and it is strongly desired to improve colorants.
Thermal transfer recording includes a recording system where a thermal transfer material having a thermofusible ink layer formed on a support (base film) is heated with a thermal head to thereby melt the ink for recording on an image-recording material, and a recording system where a thermal transfer material having a transferable dye-containing dye-donating layer formed on a support is heated with a thermal head to thereby thermally diffuse and transfer the dye onto an image-receiving material. In the latter thermal transfer system, the dye transfer rate may be varied by changing the energy to be applied to the thermal head, therefore facilitating gradation recording, and the system is especially advantageous for high-quality full-color recording. However, the transferable dye for use in this system has various limitations, and only an extremely few dyes are known capable of satisfying all the necessary performance requirements.
The performance requirements include, for example, spectral characteristics favorable for color reproduction, easy transferability, fastness to light and heat, fastness to various chemicals, easy producibility, and easy workability to construct thermal transfer recording materials. However, conventional specific dyes that have been proposed as those having spectral characteristics favorable for color reproduction and having fastness to light and heat (for example see Patent JP-A 1-225592 and JP-A 63-189289) could not be on a satisfactory level, and further improvements are strongly desired.
In color copiers and color laser printers to be driven by electrophotography, in general, a toner is widely used that comprises a colorant dispersed in resin particles. The performance requirements for the color toner include absorption characteristics capable of realizing a preferred color reproduction range, especially high transmittance (transparency) required in use in overheat projectors (hereinafter referred to as OHP), and various fastness requirements under environmental conditions in practical use. A toner comprising a pigment colorant dispersed in particles has been proposed (for example, see JP-A 62-157051, JP-A 62-255956 and JP-A 6-118715). The toner of the type may have excellent light fastness, but may readily aggregate as being insoluble and is problematic in point of the transparency reduction and the transmitted color shift. On the other hand, a toner comprising a specific dye as a colorant has also been proposed (for example, see JP-A 3-276161, JP-A 2-207274 and JP-A 2-207273), and the toner of the type has high transparency and is free from the problem of color shift contrary to the above, but is problematic in point of the light fastness.
An inkjet recording method has been rapidly popularized and is being developed further more, since its material cost is low, it enables high-speed recording, it is noiseless in recording operation, and it facilitates color recording.
The inkjet recording method includes a continuous system of continuously jetting out ink droplets and an on-demand system of jetting out ink droplets in accordance with image information signals; and the jetting system includes a system of jetting out ink droplets under pressure given thereto by a piezo device, a system of jetting out ink droplets by generating bubbles in ink by heat, a system of using ultrasonic waves, and a system of electrostatically sucking and jetting out ink droplets. As the inkjet recording ink, usable is water-base ink, oily ink, or solid (fusible) ink.
The requirements for the colorant to be used in the inkjet recording ink are that it well dissolves or disperses in solvent, it enables high-density recording, its color is good, it is fast to light, heat, active gases in the environment (e.g., oxidizing gas such as NOx, SOx, ozone), it is fast to water and chemicals, it may well fix in image-receiving material and hardly blurs it, it is well storable as ink, it is nontoxic, its purity is high, and it is inexpensive and easily available. However, it is extremely difficult to obtain a colorant that satisfies all these requirements at a high level. In particular, it is strongly desired to obtain a colorant that has a good magenta color tone, has high solubility, and is fast to light, humidity and heat, especially highly fast to light.
A color filter is required to have high transparency, for which, therefore, employed is a dyeing method of coloration with a dye. For example, a method that comprises patterning exposure and development of a dyeable photoresist to form a pattern, and then dyeing it with a filter color dye is successively repeated for all filter colors to produce a color filter. Apart form the dyeing method, a method of using a positive resist may also be employed for producing a color filter. The color filters produced according to these methods may have high transparency and excellent optical properties as using dyes, but their light fastness and heat fastness are limited. Accordingly, a colorant having excellent fastness and having high transparency is desired. On the other hand, a method of using an organic pigment having excellent light fastness and heat fastness in place of dye is widely known, but pigment-containing color filters could hardly have good optical properties like those of dye-containing color filters.
Common to those for use in the above-mentioned applications, the dyes are desired to have the following properties. Specifically, they have a color favorable for color reproduction, they have an optimum spectral absorption, their fastness such as light fastness, moisture fastness, chemical fastness is good, their solubility is high.
For use in thermal transfer recording, dyes having a specific arylidene-pyrazolone skeleton have been proposed (for example, see JP-A 2-3450). However, the dyes could not always satisfy the above-mentioned requirements for their properties on a satisfactory level, and further investigations are desired.